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‘We think the beneficial effects observed might be due to the fact the nuts provided high levels of folic acid and, in particular, essential fatty acids like omega-3 and omega-6.

‘These components tend to accumulate in neural tissue, particularly in the frontal areas of the brain, which influence memory and executive functions.’

To uncover how eating nuts during pregnancy affects a child’s future development, the researchers analysed more than 2,200 mother-child pairs living in Asturias, Guipuzcoa, Sabadell or Valencia.

During the women’s first and third trimesters, they completed questionnaires on their eating habits, which included their nut intake.

The children’s neurodevelopment was assessed via several ‘internationally validated standard tests’ at 18 months, five years and eight years old.

Results – published in the European Journal of Epidemiology – revealed the biggest benefit occurred in the group whose mothers ate the highest amount of nuts, with a weekly average of just under three 30g servings.

This is lower than the three-to-seven servings a week that is recommended in the healthy eating guide published by the Spanish Society of Community Nutrition.

‘This makes us think if the mothers consumed the recommended weekly average the benefits could be much greater,’ Ms Gignac said.

Health authorities in the UK and US do not have specific guidance on how many nuts we should be eating. However, the United States Department of Agriculture and the World Health Organisation both advocate them as part of a healthy diet.

Despite the benefits of eating nuts during a woman’s first trimester, the same effects were not seen when the mothers munched on the snack later on in their pregnancies.

Study author Dr Jordi Júlvez, assistant research professor at ISGlobal, said: ‘This is not the first time we have observed more marked effects when an exposure occurs at a specific stage of the pregnancy.

‘Scientific literature speculates the rhythm of foetal development varies throughout the pregnancy and there are periods when development is particularly sensitive to maternal diet.’

The researchers stress that due to this being the first study to explore the effects of nuts on a child’s neurodevelopment, the results should be treated with ‘caution’.

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‘We must work on reproducing them in the future with more cohort studies as well as randomised controlled trials,’ Dr Júlvez added.

Other studies have linked nuts to everything from low blood pressure and a reduced risk of diabetes to slower cognitive decline. (DailyMail)